1. Field of the Invention
This invention pertains to safety apparatus, and more particularly to apparatus for preventing a movable carriage from tipping under the influence of an overturning force.
2. Description of the Prior Art
It is well known to employ mobile filing and storage systems in buildings in order to conserve expensive floor space. For example, movable book shelves are commonly installed in libraries and offices. A mobile storage system normally includes various combinations of stationary and movable storage units. A typical movable storage unit comprises a carriage mounted on wheels which roll longitudinally along rails embedded in the building floor. The carriage is usually quite high and deep, but it is quite narrow in the direction of longitudinal movement along the rails. Consequently, the carriage is relatively unstable in the directions of motion, particularly if it is eccentrically loaded near the top.
To increase the stability of a mobile storage system carriage, the carriage frame may be designed to maximize the longitudinal spread between the support wheels. Even with the maximum spread between the wheels, it is still possible for a carriage to tip under certain unusual circumstances. For instance, tipping is possible if a wheel of a top-heavy moving carriage strikes an object on a rail; the inertia of the carriage and stored materials may cause the carriage to tip.
Certain devices are known which prevent longitudinal tipping. Such devices employ a keeper plate of some type which is fastened to the carriage and which slides under an elongated restraining bar or similar piece fastened to the rail. Prior devices suffer two major handicaps. The first is that the separate piece or bar fixed to the rail entails undesirable material and assembly expense. Secondly, prior keeper plates are difficult and costly to assemble to the carriage in accurate alignment with the rail bar.
Thus, a need exists for a mobile storage system anti-tip device which is quickly and accurately mounted to the movable carriage and aligned with the fixed rails.